


Love in the Lab

by Frazie



Category: Undertale (Video Game)
Genre: F/M, Fluff, Nothing too kinky or anthing, SansxFrisk - Freeform, Scientist Sans, Short Story, Smut, This is the only chapter
Language: English
Status: Completed
Published: 2016-12-25
Updated: 2016-12-25
Packaged: 2018-09-11 22:28:56
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,302
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/9037487
Author URL: https://archiveofourown.org/users/Frazie/pseuds/Frazie
Summary: It's Christmas Eve and its in the evening, and Frisk drops by at Sans' lab. Originally to drop off dinner, but Sans has different ideas. ;D(Smut warning!)





	

**Author's Note:**

> Hello peeps! This is just a gift for my audience in my other story A new start. Frisk is still a kid so its gonna take a while till they get the SMUUUUUUUT.
> 
> So for Christmas, here's some fluffy smut. :>  
> NOW. This will be the only chapter, Please don't be like, when will you write the next chapter?! x.x
> 
> Smut warning again!  
> Nothing dirty and kinky how I've seen some people write.No blind folds or ropes.
> 
>  
> 
>  
> 
> Oh gawd, what have I done....Imma give myself a nose bleed. 0-0

Sans pasted around his lab, reading documents over that Gaster had left for him. Gaster finally listened to Papyrus’s whining and took a break. Just the two of them, father and son. Alphys was away on the holidays with Undyne. Probably going to come back somewhat beaming spending time with her girlfriend. 

The lab was only for Sans for a while. He and Frisk lived together. They were basically married at this point, and they would be, though Sans didn’t know how to pop the question.  
Sans sighed as he’s been thinking on it, but he kept on imagining Frisk slap him and curse him out for asking such a thing.

Taking a human’s hand in marriage, just seemed impossible. Not to mention, it was the day before Christmas eve. He already chose his gifts, so he didn’t think too much on it. But how his relationship with Frisk had his brain a mess. So he went to the Lab to get his mind off things, but it hasn’t really been working.

He shuffled over some other pages before being grabbed out of his state peace. A small sound emerged, it was his text ringtone.  
Frisk’s name and picture popped up. The sight of her immediately brought a smile to his face as a light blue blush spread under his eyes.

He finally put down his papers, and let his work drift away. He picked up his phone and unlocked the code. 

_Frisk- Hey Sans! Would it be okay if I stop by to bring over some dinner?_

Sans smiled once again. How had a woman like Frisk ended up to be his? He took in a big breath and exhaled.

_Sans- Heh, Yea, c’mon down to my lair._

_Frisk- Oh my gosh. Okay, I’ll be over in a little, Dr.Evil. xp_

_Sans- Wow. See ya soon Babe._

_Frisk- See ya Sans._

Sans grinned and shook his head at Frisk’s pun. There was no way he could love her more. Sans walked around pondering on what jokes to say and what to do. Around 15 minutes later, Frisk knocked on the door. 

Sans shuffled to the door, opening it eager to see Frisk after all his work. The door swung open with frisk holding a basket with her. She greeted him with a big smile. Her long brown hair pulled back into an up and down hair do. She was wearing a dark blue greyish trench coat, with dark leggings and a jean skirt, with dark grey boots. She held a basket that held his dinner that she prepared just for him.

“Hey sweetheart” Sans said narrowing his eyes into a relaxed face. “Hey Sans.”Frisk said with an excited smile already on her face. Her blue eyes already lit up the room as she stepped in. Sans stepped aside until shutting the door when fully in. 

Frisk turned to Sans with gentle eyes. “So should I leave this somewhere? Or-” She said, signaling to the basket.

Sans’s mind lit up. What did she mean? Were they going to do ‘something’ in the lab? Or was she just gonna spend some time with him? (God, I’m such a pervert) Sans thought to himself. “Uh, yeah, you can put it on the table over there.”

Frisk followed his hand pointing towards a nearby table and walked over to it, placing her basket down. She felt her cheeks go warm as she turned to Sans. She had already seen him in a lab coat and his reading glasses, but he looked so good in it. So much more mature and smart. He always looked handsome, but something about labcoats complimented his form very well. He looked just like his father.

“Well, I best be on my way.” Frisk said with a smile, but definitely not happy to leave Sans. “You’re not gonna eat with me?” Sans nearly exclaimed stepping in front of Frisk, blocking her path. “Well I don’t wanna interrupt your work, you seem busy.” Frisk’s cheeks tinted a lovely red as she looked away from Sans, poking her two fingers together.

“Babe, I can take a break. I wanted to see you.” Sans said, bringing his hands onto her arms in a comforting touch. “Alright, I’ll go get my food!” Frisk said with red cheeks but once again happy. “Food?” Sans questioned, but his confused gaze, nearly instantly changed to a shit-eating grin. 

“Frisk...Did you come here to originally have dinner with me?” Sans said with his smile widening at the sight of Frisk’s red face. “Well...uh...I- might have...had an idea of eating together…” Frisk said looking at the ground again. “Heh heh, Cute.” Sans chuckled. Which of course, Frisk pouted. She didn’t really like being called that.

Frisk left the lab to retrieve her food, while Sans went into the lounge with his food. His hands entered the basket wondering what she packed. Of course, there was a super deluxe ketchup that had his name on it. He smiled on how much she knew him so well. Especially deluxe.

He brought out some more food and set it all on the table. Frisk soon came into the room, holding her own basket as well. “I'd appreciate if you not stare at me like that.” Frisk said pouting.

“Oh...like what?” Sans narrowed his eyes as his shit-eating grin widened.

“You know what I mean!” Frisk blushed harder, as she took a seat. Sans chuckled again.

Soon enough they were stuffed with food. They both sighed satisfied with Frisk’s cooking.  
It was around 9:40 at night, but for some reason, Sans was barely tired. His mind has been on...other things.

Frisk yawned slightly. “ That was good.” Frisk sighed.

“Heh, yea. Looks like there’s a new Rachael Ray.” Sans joked. Frisk smiled as a light dust of pink appeared on her face from the compliment. “Well, I’ll clean things up and you can get back to work.” Frisk said as she got up. “Uh- I don’t have to get back to work immediately.” Sans stated, getting up as well. 

“It’s alright Sans, I should be leaving anyway…” Frisk said with an understanding smile. “Frisk-!” Sans yelled,grabbing her arm, slightly startling his beloved girlfriend. Frisk gave him a face that read “What’s wrong?”

His face turned blue as he decided he wanted to tell her. “I- uh. I don’t want you to go home.”  
Frisk blushed harder. She knew exactly why Sans didn’t want her to leave.But it was like she didn’t remember any other time they did it. It wouldn’t their first time or anything, but both felt like it was despite their first was last time. 7 months ago..

Sans stepped closer and cradled Frisk in his arms, though she faced away from Sans. He had always been bigger, but he always loved the size of her compared to him. She was around the height of his shoulder. “It’s been so long since our time Frisk.” Sans said in a deep husky voice.

“Uh- ah!” Frisk suddenly moaned in surprising pleasure. Sans’s hand covered one of her breast as he lightly squeezed it. “S-sans...ah...” Frisk moaned again covering his hand with her own as he slightly massaged it.

“Sans. We can’t do this here.” Frisk said intertwining her fingers with his slightly pulling his hand away. “Frisk… I missed our night.” Sans whined, hand returning to her chest.

“What if Gaster walks in on us?” Frisk said with caution. “He’s on vacation with Paps.” Sans said, continuing to fondle her breast.

“W-what about Alphys...A-and Mo-om…ah…”Frisk tried to speak normally but it was almost impossible with Sans touching her like this. “She’s taking a break from work for the holidays as well, and Tori told me she’s spending some time with Asgore and Flowey. Same for Mettaton, he’s also away for the holidays.”

“B-but what if-” Frisk stammered. But was silenced by Sans unbuttoning her blue dress shirt.

“It’s okay Frisk, I locked all the doors. We’ll be fine.” Sans whispered as his hot breath brushed her ears.

“Ah...I see...Are you sure it’s okay at your lab? Ah!” Frisk shrieked in delight. Sans’s hand crept up her stomach, up to her breast covered with her bra. “mhm…”Sans hummed. His other hand crept down to her skirts button, and slyly unbuttoned it. 

His eye sparked up as blue flames licked his skull. He lifted Frisk almost instantly with his magic. This way he could easily get off her lower clothes as her waist was right in front of his face. “S-Sans!?” Frisk yelped. As he tugged at the fabric around her body, her dress shirt slipped off along with her skirt and leggings. She was put back down in the first position.

His head settled in the crook of her neck, tongue appearing out to lick at her sweet spots. Slightly nipping while at it. He especially loved biting her with his fangs, only gentle nips though. “Ah…”Frisk slightly moaned as Sans continued with giving her his sweet markings. Sans finally stepped away momentarily. Sans’ s hands followed the trace of her bra. He felt all the designs of the fabric, but his gaze finally met the hook. 

Another hand came for assistance and soon enough it was unhooked. The bra became loose around her torso, exposing her lovely back. Sans’s hands pulled down her straps finally allowing the fabric covering her chest fall and expose her beautiful breast. 

Frisk blushed a lovely red as she closed her eyes in embarrassment. His hands finally returned to her chest as she let out a pleasure sigh. His thumb bone tweaked the small bump. “Ah!” Frisk moaned. He continued to fondle and massage her breast as her moans were like music. 

As his hands continued in a circular motion, her moans got more sweet. Every once in while she would make a small whimper or sigh in pleasure. After a while of just kissing the back of her neck, and massaging her breast, he got tired of standing. Frisk was in the air like that, Sans held her body princess style, carrying her to the couch while he then he got on top of her.

Frisk blushed even harder seeing Sans on top of her. Soon enough his hands were back on her chest followed by his tongue. Frisk quietly groaned as Sans’s hand slid down her body, following her lovely curves. Until he stopped at her panties. He tucked his boney fingers under the cute fabric with many frills. He even went so far to kiss the front of her camel toe. “Mmmh…”Frisk sighed lovingly smiling in pleasure. 

“Heh. These panties are quite cute...Did you dress up on purpose? Just for this.”  
Sans said with a smug smirk. Frisk jolted up as like a bolt of lighting. “Of course not-! Ah!

 

Frisk was caught off by Sans leaning forward and taking the small bulge of her breast into his mouth as his tongue met her smooth skin tinted with a pinkish brown. “Sans- ah! Ah…” Frisk moaned again. His wide magic tongue caressed her small nodules just perfectly. Rubbing them up and down, side to side, then in circles. He knew exactly how to make her feel good. He took one of her nipples in between his teeth, rolling it sweetly. When done with one breast, he moved to the other, rolling the previous one with his hands.

Frisk hummed in pleasure as Sans worked his way on her chest. One hand swept over her body. Slightly hovering over her belly, going lower to her cameltoe. Frisk slightly pressed her legs together, slightly scared on her second time with Sans, but soon enough, Sans’s hands slipped under her panties, finally touching the warm smooth skin hidden from him. 

“Mmph…”Frisk whimpered, eager for Sans to cease his teasing. His hands went even lower until he met the start of her lips. Sans leaned back, taking out his hands from her panties and freeing her chest from him. His hands took the hem of her panties and slightly tugged. Frisk got the idea and slightly lifted herself to let Sans slip her underwear off. Just like that, her underwear slid off and he tossed it to the side.

He set his hands on top of knees and looked back at Frisk’s lovely red face, knowing what he was doing. Slowly, he spread her legs open. Letting him get clear shot of her wet lips in between her thighs. He grinned and narrowed his eyes. He almost looked like a hungry dog about to receive his food.Frisk blush harder from Sans just staring at her body.

Suddenly Sans brought his hands to her lips and slightly spread them apart. She tried to press her legs back together out of embarrassment, but Sans held her down with his magic. Her legs were far apart,and there was no way she could put them back together.

“You’re _wet_ Frisk.” Sans growled. “Mmph! Ah-aa~” Frisk moaned as Sans’s tongue lapped over her inner lips. Her hand slapped over her mouth from becoming too loud, it didn’t seem fair she was the only one making sounds. Sans did not agree with this at all, and grabbed both of her wrists with his magic. 

Bounding them together, Sans’s magic pushed frisk Down, pinning both hands above her head. This way, she was completely powerless. She couldn’t stop nor move away, not even cover her moans. “Sans~! Th-is -sn’t fair! Ah!” Frisk threw her head back in pleasure as Sans’s tongue continued its caressing.

He brought his hand up to her entrance, and pushed two fingers inside of her, being rewarded delicious moans from Frisk. She was even smiling from his fingers. He pumped the two in and out of her body, as for his tongue went up and found her clit.

Frisk gasped in delight. Her hands clenched into fist and sweat started to fall, making her body slick. She felt herself getting wetter and wetter and felt the build up start. Her body started to squirm even though she couldn’t move too much, as she was pinned. “Ah! Mm~ Haaah...~” Frisk nearly screamed from Sans touches and kisses. All of a sudden Frisk felt an even bigger rush around her erect nipples. Sans summoned more magic and set it to her breast, having the same feeling of him sucking, licking, nipping at them.

“S-sans! I-I’m gon-na cu-cum!”Frisk screamed. Sans continued, a bit rougher than before. Seconds later, Sans backed and finally she came. Her head swung back, hitting the couch. Every muscle in her body tightened. Her heart-beat increased as her breathing got heavy.

After the earth-shattering moment, her slick body collapsed onto the soft couch as her breathing was short and jagged.

Sans stood up, looking down at the harshly breathing girl. Hair sprawled on the couch, arms and hands above her head, legs far apart in a way so inviting. She hadn’t noticed that his magic had dissipated and she was spreading them on her own now. But her hands were still pinned.

His lab coat and glasses were taken off and he carried them with his magic to be set on a nearby table. “Hey babe, flip onto your hands and knees, I wanna try a new position” Sans said, voice low and husky. Frisk nodded after calming down. She sat up when he released her. And she flipped over onto her knees. 

She lied back down, pulling a nearby pillow to lie on, though her knees kept up, exposing her bottom and dripping entrance. Her hands grabbed the pillow, eagerly waiting as Sans stared at her perfect body that belonged to him. 

 

His eye flared up even brighter at the sight of her. He freed himself from his pants, which a blue bulge was barely contained by his boxers. He crawled onto the couch as well and set a hand onto one of her thighs. Walking now on his knees, he got closer, until the tip of his length. He slid it up and down, in between her folds, covering it in her sweet juices.

When it was nice and slick, he slid it back up, meeting her entrance. Slowly, he pushed it in. Frisk’s body clenched at how thick it was, the first time, she worried it wouldn’t fit. Around half way in, Sans pushed it in a bit faster, All Frisk did was push into him. “Mmmph!” Frisk moaned when Sans gripped her hips and and finally made his first pump.

“Oh!...hah~!...”Frisk sighed as Sans began to pump in and out of Frisk. He made a quiet groan sound but wasn’t nearly as loud as Frisk’s moans. Everything was silent, except Frisk and Sans.   
After a medium speed of thrust, Sans began to go faster trying to go in as deep as possible. Finding her G-spot was a golden treasure though. He finally began to hit it instead of going deeper, and Frisk screamed.

“Oh my God! Ah~! Righ-t the-heerre~ Ah~!” Frisk yelled, squeezing the pillow tighter. Sans leaned forward, not stopping his thrust, but laid on to of her. It allowed for his rib cage to be brushed against her warm back, and he had full access to her body. His hands slipped around her torso and he again a started to fondle with her chest. “Sa-ans! Ah!” Frisk screamed when his hand went down to her folds and began to rub her clit. “Y-yes! Ah! Mo-ore! Oh my gosh~!” Frisk stammered, she could barely even speak,it felt so good. She was reaching her limit and was going to climax soon. He started biting and licking her back and neck. While more pulses of magic rushed in all of her sensitive spots. 

“N-no! If you do that, I’ll- ah! I’m gon~na- Ah-hahhh! I’m gonna cum a-gain! Sa-a-ans! Nng!” Frisk screamed as Sans pounded into her. Sans was reaching his limit as well. His teeth clenched when his mouth left her skin. He felt his magic start to get out of control. “M-me too!” Sans groaned, fastening his pace trying to climax as hard as possible. 

Finally. Frisk came again, with Sans not short after.”Urk!” Sans groaned as he let himself cum as well. Filling her with his bright cyan liquid, it nearly made Frisk scream again all on her own. He basically collapsed on top of Frisk, exhausted. Both of their breathing was jagged and heavy.

“That was amazing~.” Frisk said, sounding exhausted, but happy. Sans chuckled at her comment. “Glad you liked it~”

“‘Like’ is an understatement~”

Sans chuckled again, before showering her back with kisses. “See? If you would have left, you would be home all one waiting for your beloved boyfriend to come home” Sans teased. Frisk slightly blushed but rolled her eyes.

Frisk suddenly saw a flash of blue and just like that, she was on her back again. “Sans??”Frisk asked embarrassed. She was met with Sans without his shirt, or pants, and his length was already hard and tall again.

“S-” Frisk stuttered. “Ready for round two?”Sans growled, voice husky yet predatorial.

Frisk blushed even harder when his tip was already at her entrance, but her smile instantly turned into an ‘Oh, alright!’ look with her own grin. She leaned forward and wrapped her arms around his neck, as he sat her onto his lap and girth.

“O-only because it’s Christmas, b-one he-ad...Ah~”Frisk groaned in his skull. “Mhmm…”Sans purred back but decided to nip at her earlobe and neck. Frisk hummed in response. All out of pleasure.

The couple then had a night filled with nothing but love and passion. Both got what they wanted for Christmas. Eachother.

**Author's Note:**

> See!? That wasn't too bad right???
> 
> Shit. It probably was from the pinning Frisk down thing. hhhhh
> 
> Merry Christmas everyone!


End file.
